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Digitrax DS54
Digitrax DS54 Quad Stationary Decoder for Digital
Command Control with Programmable LocoNet Input/Output
(buy)
General: The Digitrax DS54 is the most
comprehensive decoder of the group. It has more options than any
of the others, and has the capability to do some stunning layout
effects, such as complete operation of a crossing gate. It has
feedback to the LocoNet cab bus that carries position data, and
has the capability to accept multiple trigger inputs from track
detectors, push buttons, etc.
There are four independently programmable outputs
arranged in decreasing successive address order from four times
the baseline address of the decoder. Each output has a green common
with a black and a yellow signal output. Each output can be set
to one of four modes.
- Retriggerable pulse of programmable length
- Non-retriggerable pulse of programmable length
- Continuous output
- Blinking
Retriggerable and non-retriggerable pulses are the
same except that the retriggerable can be lengthened if another
trigger occurs before the pulse is finished, while the non-retriggerable
cannot be extended. The pulse output will appear between green
and black or green and yellow depending on the whether an ON or
OFF signal is sent to the decoder. The pulse mode is used generally
to control a twin coil switch machine such as the Peco. Green goes
to the common, yellow goes to one coil, and black goes to the other
coil. If the switch works backwards, then reverse black and yellow.
The pulse is set to the shortest pulse that will throw the switch
machine.
In the continuous mode, the output is always on.
It is on from green to black for one command, and is on from green
to yellow for the other command. It is kind of on from yellow to
black or from black to yellow, changing polarity with the input
command (see below under performance). The continuous mode is for
stall current switch machines and similar types of loads.
Finally, there is the blinking mode. In this mode,
black to green is on and yellow to green is off in one time period,
then they switch with yellow to green on and black to green off.
The on and off time are equal, but the length of time is programmable.
An off command has everything off. An on command starts the blinking.
This mode is used to operate a crossing flasher with alternating
flashing lights.
The DS54 has 8 trigger inputs that can be programmed
to perform various tasks. A trigger input detects when a particular
action has occurred (such as the locomotive entering a block) and
causes some other action to occur (such as causing the output connected
to a signal to switch from green to red). The inputs can be set
to respond either to a constant voltage level or to respond to a
changing voltage level, depending on the desired function. The
relationship between the inputs and outputs is completely controlled
by the values programmed into the unit’s Configuration Variables
(CV’s).
Connections: Input connections for triggering
functions are via a standard Digitrax 9-pin connector. Outputs
are connected to loads by a four-wire standard telephone type connector
(red, black, yellow, green). You can go to the hardware store,
by one cable, cut it in half, and you have two output cables. Both
input and output cables and connectors are included with the DS54.
Track connections are by two #6-32 screw terminals. The interface
to the LocoNet is a standard RJ12 connection. The auxiliary AC
power connections are made to a red/black wire lead pair that comes
already soldered to the printed wiring board.
Feedback: All of the functions listed above
will work with any DCC system (assuming you can get things programmed).
If your DCC system is Digitrax with LocoNet, then there are additional
functions available. These are feedback functions, and they allow
the command station to receive information from the decoder and
allow the decoder to issue commands on the cab bus in the same way
as the cab itself. One type of information is turnout position.
By feeding position feedback to the command station, the cab can
display the turnout position on its display. Another example actually
allows one switch to control the position of another switch. In
this case, when you throw switch #1 on your layout, the decoder
at the switch #1 address can contain directions that will send a
message to the control station to also throw switch #2. Switch
#2 can contain instructions for switch #3, and etc. In this manner,
a single action can be cascaded. In the example, it may line up
a particular switch route. As another example, a switch can be
wired to a trigger input on the decoder, and programmed to issue
a RUN/STOP command to the layout based on switch status. There
are also commands for the control of a self-indexing turntable,
and for the linking of signals in a CTC setup. This discussion
is not exhaustive, but should give you a good idea of the capabilities
of the DS54.
Programming: The first thing to remember about
programming the DS54 is that all the variables are hexadecimal numbers.
These are numbers based on 16 instead of 10. The manual contains
a conversion chart, but you must pay attention to the values that
you are entering.
Any DCC system that has accessory access can program
the base address of the DS54. The address button on the unit is
pressed and then a switch command within the desired address is
sent. The unit will set the decoder addresses based on this data.
For all other programming, either a Digitrax system must be used
or you can use the Digitrax PR1 programmer (review of the PR1 is
also available on Tony’s site). I tried programming the DS54 with
my NCE system. On the programming track, the NCE system could not
read the CV data. When I programmed the CV data and then read it
back using the PR1, it did not appear that the correct data had
been stored. The NCE system did, however, correctly modify the
base address of the unit as described above.
On the DS54 printed wiring board are two link pins.
These pins must be linked in order to program any CV, and must be
unlinked for normal operation. Programming must take place on the
programming track, and must be done with no loads, inputs, etc.
connected to the unit (an exception is the special load used to
allow CV read back). Programming the DS54 can be a daunting task,
particularly since you need to keep track of all your options as
digital numbers. I found that the PR1 made programming the DS54
much easier. The PR1 has a special programmer function for the
DS54. All the options are available through drop down boxes that
allow you to select the exact options that you want. Once you have
set things up, a simple SEND will correctly program a DS54. The
PR1 also allows you to read back the programmed data. If you forgot
how you set up a particular unit, the PR1 lets you quickly determine
what you did rather than sorting through hexadecimal numbers CV
by CV. If you are going to use the DS54, I strongly recommend the
use of a PR1 programmer.
Manual: The manual for the DS54 is well done
and complete. Since the unit itself is quite complex, the manual
also contains a lot of information. I recommend several reads through
the manual before you touch hardware. The manual is very good at
taking you step by step through the DS54 from simple to more complex
functions. Throughout the manual are very clear hookup drawings
and step-by-step programming instructions. Once you have digested
the manual, you will have a very good working knowledge of the DS54.
Performance: The DS54 has two input terminals
for auxiliary AC input. If no AC is supplied, the accessories are
powered by the track DCC. I tested things both with and without
auxiliary power.
Surprisingly, the first load that the DS54 had trouble
with was the Tortoise™ slow motion switch machine. The manual does
mention that this is a problem. With the selected output set to
continuous and the Tortoise™ connected from black to yellow, the
Tortoise™ ran, but VERY slowly with very little torque. The run
voltage was 6.1 volts, while the stall voltage was 3.1 volts. This
was very marginal operation at best. As recommended by the manual,
I connected a 470 ohm resistor from yellow to green and from black
to green. Now the Tortoise™ ran much better! I measured 10.5 volts
run and 7.4 volts stall. Not quite the desired stall torque, but
certainly acceptable. I tried the Tortoise™ without the resistors
but with external 15.1 volts AC power. Again, the unit ran acceptably
well. I measured 12.7 volts run, but only 5.0 volts stall, so the
stall torque in this configuration is still not very good. It seems
that external components are required to make the DS54 work with
stall motor switch machines. This requires a more complex installation.
I wondered if I could limit the liability a little by combining
functions. The 470 ohm resistors supply about the same current
as the grain-of-wheat bulbs, so I connected one bulb from green
to yellow and one bulb from green to black. That worked quite well.
Now I got 11.4 volts run and 9.2 volts stall, about where it should
be. In addition, the lights acted as a position indicator, alternately
lighting as the switch changed position. The lamps had 11.4 volts
across them when active in this configuration. I believe this is
the best configuration to use if you are using the DS54 with a stall
motor switch machine such as the Tortoise™.
I could not get the DS54 to operate the Nick & Jack International switch machine. I tried DCC and auxiliary AC power,
and I lengthened the pulse to 4 seconds. The best I could get was
a subdued buzzing noise.
The Peco switch machine worked fine with both DCC
and auxiliary AC power. I used a 0.5 second pulse, and it was more
than sufficient. It may depend on the specifics of the switch to
which the machine is connected, so you may have to adjust the pulse
width a little with your setup. I noticed that the Peco worked
with significantly more force when I used external power. The source
voltage goes from about 11.6 volts on DCC to about 19.3 volts on
my 15.1volt AC source. The higher voltage gives more magnetic force
and snappier switch operation.
I wired the grain-of-wheat bulbs both with one lead
to green. On one lamp the other lead went to yellow. The remaining
lead went to black. If I programmed the CV to one of the blinking
rates, the bulbs alternately flashed, as in a crossing signal.
The flashing could be turned on and off by DCC command. When I
programmed the CV to constant, then I could turn on one lamp or
the other in succession. In other words, this mode is used to control
a two-lamp signal. When I ran the lamps from DCC power, the voltages
were just about right: 11.4 volts. Slightly under powering an incandescent
lamp will result in greatly extended life. However, when I used
my 15.1 volts AC auxiliary power, I found that the lamp voltage
had increased to 19.3 volts. This voltage is much too high for
these lamps! They look very bright, but they will die within hours.
If you are going to use external power with the DS54, either decrease
the AC voltage (which will reduce the effectiveness with switch
machines, etc.) or use higher voltage lamps in your lighting circuits.
A third alternative would be to include a series resistor sized
to drop the lamp voltage to the correct range. A final solution
is to use a red, green, or white LED for the lighting effects and
size the series resistor to give the correct LED current with the
actual DS54 output voltage. To calculate the resistor size, divide
the output voltage in the lamp mode by 0.025. This will give you
the minimum resistor value in ohms that you can use. Up to 25%
larger in value is probably OK.
I was unable to get the accessory motor to operate
with either DCC power or auxiliary AC power. I measured only 9.6
ma at less than 1 volt across the motor.
Recommendation: The DS54 is a BEST CHOICE
for layout automation. If you want to set up a crossing gate tripped
by a track detector or if you want to have your CTC signal system
function automatically as the train enters a block, then the DS54
is the definite choice. If you already have a Digitrax system,
the feedback capabilities of the DS54 will work seamlessly with
your controller display to indicate switch position when you select
a switch. The cascade capability will simplify setting up complex
switch routes. It will work well with a Peco style snap action
dual coil switch machine. The DS54 will easily operate incandescent
lamps and LED’s, but extra hardware is necessary to get adequate
performance with a stall motor switch machine.
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